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Binocular Space Telescope in the Works

Posted by michael on from the biclops dept.

museumpeace writes "ABCNews.com's technology pages have a story about NASA's plans to orbit a binocular telescope. Similar in concept to the Arizona telescope reported in /., this new variable baseline interferometer would be able to operate in the UV which is unavailable to terrestrial intstruments. The telescope would have the resolving power of a 120 foot diameter conventional telescope."

8 of 30 comments (clear)

  1. Wow. by francisew · · Score: 2, Interesting

    This is pretty neat. Low IR interference would be great. There is so much heating/cooling from exposure/shadow cycling as satellites orbit the earth that I'd guess it have cyclic noise.

    They never really mentioned how high it would orbit.

    120 feet of rail is a lot. I wonder how prone it'll be to damage?

    The other telescope mentioned in the article seemed more interesting. Even though it's 1/4 the length, it had interferometers on board, and would probably be more useful for spectroscopic purposes.

  2. Why binocular? by DrKyle · · Score: 3, Interesting

    I can understand that getting a nice pair of binoculars gives you a sense of depth perception, but when you are looking at something 50 light years away does it really make a difference that you take measurements from 120 feet apart? I mean they could just time lapse the images and then compare them as the Earth is moving way faster, as we are moving around the sun at about 1800 kilometers per second. So really, what good is 120 feet?

    1. Re:Why binocular? by Mark+of+THE+CITY · · Score: 2, Interesting

      If you really wanted near-simultaneous binocular imaging to capture some 'fast' event, maybe you would want two cameras in solar orbit. At Earth's orbital radius (9 light minutes), for example, that would give you about 18 light minutes of separation.

      I doubt there's a burning need for this, though.

      --
      The clearance system sounds logical. It is not. It is completely arbitrary. -- John Bolton
    2. Re:Why binocular? by Doctor+Fishboy · · Score: 4, Informative
      but when you are looking at something 50 light years away does it really make a difference that you take measurements from 120 feet apart?

      It makes a big difference. The aim of the game is to increase your angular resolution, and interferometry is a way of combining two separate telescopes to get the angular resolution of one larger telescope.

      You cannot take one image, wait a few seconds to get a baseline, and then take another image. For the technique to work, you need the two images to be recorded with phase information, and for wavelengths shorter than radio waves, you cannot easily and efficiently do that.

      For a 8.4m single mirror, the 125 feet separation increases the angular resolution by a factor of 6.25. That's a very useful improvement.

      The problem is that the light from the two mirrors has to be cophased to within 1/10 of a single wavelength of UV light. Those tolerances are absolute bastards to achieve, even in outer space.

      Dr Fish

    3. Re:Why binocular? by deglr6328 · · Score: 4, Informative

      They're not really using it for "binocular vision", they're using it to do "aperture synthesis" or optical interferometry where the separation of two telescopes whose optical paths are combined (with sub wavelength (like 550nanometers for green) precision maintenance of the optical path) effectively allows it to have the resolution of one humongous telescope whose mirror is as big as the separation between the two smaller telescopes or "baseline". Radio telescopes are combined in the VLBA or very long baseline array like this, except that they are not connected to eachother as they make observations (at least not until recently) so they record the phase of the radio waves as correlated to a high precision atomic clock standard, then combine the (usually terabytes of) data from each dish later on supercomputers. None of this comes across terribly clearly in the article because the journalist who wrote it is an idiot("SPIRIT telescope since it will be detecting infrared light, which is a light form of heat." uhhhh yeah.).

      --
      - "Hear that?! The percolations are imminent! Cease your ingress!"
  3. Speaking of that exposure cycle... by PedanticSpellingTrol · · Score: 2, Interesting

    Why not build a network of telescopes on the lunar surface? 14 days without solar exposure, a stable platform, no atmosphere... seems perfect.

    1. Re:Speaking of that exposure cycle... by bitingduck · · Score: 3, Informative

      This seems to come up every time there's a space telescope article. The moon's not that great a place-- it's not as stable as you think, it's dirty, you get cycled in and out of full sunlight, and you have to land everything softly in a nasty gravity well without any atmosphere to use for braking.

      I'm going to have to put in a journal entry or something with why the moon is overrated for space telescopes.

  4. re: Wow by bitingduck · · Score: 2, Informative

    from looking at the sunshades, I'd guess that they plan to put Spirit in an L2 or earth trailing orbit, most likely L2-- it's close enough for high bandwidth communication, and it actually takes slightly less energy to get there than earth trailing.

    The other mission they mentioned, SIM, won't do spectroscopy. It's a very high precision interferometer for astrometry-- it will measure positions of stars to a microarcsecond or so. I can't remember the down to earth comparison information, but it will be capable of detecting planets of a few earth masses in their stars' habitable zones around the nearest 250 or so stars. It will also remove the sin(i) ambiguity of the radial velocity measurements of the planets already known. There are also a bunch of other science programs covering stellar astrophysics, and some extragalactic stuff, too.